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ArcticMyst Security by Avery

vacuum fluorescent indicator tubes

phenol

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Joined
Oct 30, 2007
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533
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I had a bunch of 74' CMOS chips (nands, flipflops, counters, decoders,...)lying around and i figured i should put them to good use and build a frequency counter. It has a 1-Hz resolution and a 0.5ppm VCTCXO reference oscillator.
While looking for suitable LED 7-segment displays in the junkbox, i found an ancient VF tube from the late 70s. Powered it up and it worked, 35 yrs later. After 3 minutes of googling around I ordered 20 'new' ones, 60 cents a pop. They came in their original packaging and the date code on them is 1990. These are the USSR-made IV-3A 7-segment tubes.
The thing needs 0.7-1v of heater filament voltage and 15-20v on the grid and individual segments. 74 series only has 5v, so i had to boost the available 5v to 20+ volts and step it down to 0.8v ac for the filaments. The two tasks are performed with a HF transformer with 2 secondaries and a push-pull'ed primary runnin off of 5v. The 8 74hc4511 decoder outputs are then level-shifted to 0-20v. All in all, the array of 8 VF tubes draws two times less current than 8 small LED displays.
The tubes glow with greenish-blue color and as you can see, there is noticeable spread of output flux among different specimen. The difference doesnt look so big in real , though. It's measuring 123.45678MHz in those pics.
 

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Joined
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Very Nice ! , Love VFDs controlled with logic ICs .
 
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Joined
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Messages
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Points
83
30-ish logic ics and 56 dual npn/pnp transistors

Nice ! , I made a simple logic based 24 hour clock , but for 6 digits using npn/pnp level shifters I needed so many of them it got to big .
 
Joined
Jul 27, 2007
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And you did all of that on perfboard? You sir are nuts. I hate making circuits on perfboard once they get past the marginally complicated level.
 

phenol

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Half way through i started to have doubts and the annoyance level was way in the red zone, but it was too late to give up.
it works nicely, counts up to 150+MHz without any jitter in the LSD and thats with standard 74AC/HC socketed chips on a perfboard, well, 3 boards.
 
Joined
Dec 11, 2011
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Ditto on the perfboard insanity and wanting pics. I hate doing anything more complex than mostly DIP-8's and a couple DIP-16s on perfboard.
 

phenol

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Joined
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Messages
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The board with many chips contains counters/decoders/control logic and some analog front end signal conditioning (1 mosfet tetrode and two bipolars). The smaller board gracefully connected to it has a stable 10MHz reference oscillator and 7 cascaded 74hc93 each dividin the reference freq by 10.

Hidden under a 3D mesh of wires are 56 dual npn/pnp transistors level-shifting the 0-5v signals from the BCD decoders to 0-20V for the array of 8 VFD tubes.
The top side has more jumper wires and a step-up/down xfrm for the anode/filament voltages.
 

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Joined
Dec 11, 2011
Messages
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Points
83
At least you used pad-per-hole perfboard. You're not insane, just very ambitious, heh. I thought you might have been using old style point-to-point vectorboard at first, lol.
 




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